How does fuel injection work? This slow-mo video shows you

by Antony Ingram
23 January 2023 2 min read
How does fuel injection work? This slow-mo video shows you

Fuel injection is often seen as one of those demarcations between older and newer cars, but the technology was invented as far back as the 1870s, and mass production of diesel-engined passenger cars meant fuel injection has been used in road cars since the 1930s.

Like a carburettor, it’s basically another way of atomising fuel so it can be burned in an internal combustion engine – and to see how it works, there’s probably no better demonstration than the latest slow-motion video from Smarter Every Day.

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A couple of years back host Destin Sandlin created a video demonstrating how carburettors work, using a rudimentary but custom-built see-through carb. In that video, slow-mo shots revealed how low-pressure intake air draws fuel into a venturi, at which point it’s broken into a fine mist, mixed with the air in the right ratio for combustion – with the help of a choke, and a throttle valve.

The latest video is a little simpler, with Sandlin rigging up different types of fuel injector with a friend, and using a manual pump to send fuel through the fine nozzles at the tip of the injector.

Each of the injectors shown is taken from a tractor, with different types demonstrating different spray patterns that help or, in the case of older, more worn injectors, hinder combustion.

The really fascinating part though comes later in the video when Sandlin hooks up a blowtorch to set the fuel alight. While spectacular, it also gives an insight into the correct air-fuel mixture required for the fuel to combust – with fuel close to the injector itself not lighting, the flame front only beginning when the spray is fine enough for the correct “stoichiometric” ratio – the optimal mix of fuel and air.

This video is just part one, with Sandlin promising a second video on the way going into more depth on direct injection, port injection, throttle bodies, and electronic injection. If it’s as informative as this one, we’re in for a treat.

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